When you’ve got the best selling FPS video game of 2010, what do you do for an encore? Why, keep releasing expansion and map packs of course to enhance the experience even further.

That’s just what Activision is doing with the announcement today of Annihilation, a brand new content pack for Call of Duty: Black Ops, that’s set for release for XBox 360 on 28 June.

Annihilation will include four new multiplayer maps “Hangar 18,” “Drive-In,” “Silo” and “Hazard.” There will also be a new add-on for the popular Zombie mode, in which players must defend themselves against hordes of the undead. Of course. Who doesn’t love zombies?

“With Annihilation, Black Ops fans will get four exciting and unique multiplayer settings with Hangar 18, Drive-In, Silo and Hazard,” said Treyarch Studio Head, Mark Lamia. “Players will also enjoy an all-new Zombies experience, Shangri-La, an exotic and mysterious map filled with deadly traps, dark secrets and innovative gameplay that will challenge even the most daring Zombie hunters.” Sounds cool.

Of course, as you already know, Call of Duty: Black Ops is a huge success having grossed over $1 Billion worldwide. With content packs like Annihilation and previous releases First Strike and Escalation, it’s popularity is sure to continue. The only thing that might displace it, or at least knock it down a few pegs, is the upcoming release of Call of Duty: Modern Warfare 3 — which I got to check out recently at E3.

I’m sure there’s room at the top for both of these games. More info on Call of Duty: Black Ops Annihilation as we get it.